The present invention relates to the synthesis of chiral cis-aziridines (III) by reacting an imine (I) with a diazo compound (II) in the presence of a chiral vaulted biaryl-Lewis Acid complex.
Aziridines are versatile intermediates that have great value in organic synthesis..sup.1 A recent review on the asymmetric synthesis of aziridines reveals that nearly all non-racemic aziridines are made from other chiral materials..sup.2 Therefore, there is a need for the development of new methods for the asymmetric catalytic synthesis of aziridines.
Previous reports have focused on three different strategies to this problem. Most past effort has involved the transfer of a nitrene from [N-(p-toluenesulfonyl)imino]phenyl iodinane to an alkene mediated by a chiral metal catalyst which can result in the production of N-tosyl aziridines in good asymmetric inductions with certain alkene substrates..sup.3 An alternate method involves the transfer of a carbene to an imine which has been reported with a chiral copper catalyst.sup.4a and more successfully with a rhodium catalyst that was mediated by a chiral sulfur ylide..sup.4b A third strategy arises from the recent observation that simple Lewis acids can catalyze formation of aziridines from ethyl diazoacetate and imines..sup.5,6 However, a screen of this reaction with a variety of chiral Lewis acids failed to produce aziridines with significant asymmetric induction..sup.5c ##STR2##
Despite these advances, there remains a need for a process for producing chiral aziridines.